Try moving forward all three front speakers as much as possible.
Add acoustic treatment, foam, pillows, wall rugs etc... directly behind the three fronts. The center is probably the worst problem with the brick. Hunt around the house for anything you can experiment with.
Try turning your center channel 90 degrees on end. Keep the center tweeter level as close to the L&R speaker tweeter heights if possible. This will give you wider dispersion horizontally and less dispersion vertically. Tilt the speaker so it is aiming at the listening position.
You may need to tweak your levels after each experiment.